i#2121 date conversion: fix Windows build breakage
i#2121 date conversion: fix Windows build breakage

Fixes Windows build breakage from f708ccc.

Review-URL: https://codereview.appspot.com/315460043

AmesianX/dynamorio,AmesianX/dynamorio,AmesianX/dynamorio,AmesianX/dynamorio,AmesianX/dynamorio